1. Field of the Invention
This invention relates to a hot-melt adhesive composition which is effective for bonding at low temperatures and which affords superior heat- and solvent-resistance and water-proofness to the joined materials.
2. Description of the Prior Art
The known thermoplastic hot-melt adhesives include polyethylene ionomers, ethylene-vinyl acetate copolymers, polyesters and polyamides. Polyethylene ionomers, ethylene-vinyl acetate copolymers and polyester adhesives are inferior in their bonding strength and their heat- and solvent-resistance, although they are generally satisfactory for bonding at a lower temperature. The polyamide adhesives include homopolymers of nylon 11 and nylon 12 which are film-like hot-melt adhesives possessing good heat- and solvent-resistance and water-proofness. These latter polyamide adhesives can be used only with a limited class of substrate materials because of their higher bonding temperature. The so-called nylon copolymers which are internally plasticized so as to lower their melting point to make them suitable for low temperature bonding suffer from lower heat- and solvent-resistance and water-proofness. It is also known to apply epoxy resin films on both sides of nylon homopolymer films for improving the heat- and solvent-resistance and water-proofness of the bonded materials, or to use a so-called nylon epoxy type adhesive consisting of the nylon copolymers mixed with epoxy resin. These known adhesives are also inconvenient to use because they must be heated for a long time at high temperatures until complete setting is attained.